Studying the etiology of these two cancers and their correlation in physicians, a relatively homogenous population which is unique in having a high probability of exposure to repeated low-dose radiation and infections and good medical histories. The design is a case-control study with controls comparable by age, race, sex, and year of death selected from total physician deaths over fifteen years. An equal number of living controls will also be selected. Risk factors identified in previous studies will be examined by telephone interviews with next-of-kin, physicians associates, or physicians if a case-control. There will be special emphasis on determining the exact number of years of exposure to radiation and the estimated dose levels by year or dosimetry data. Questions concerning patient contacts, personal characteristics and medical history will be included. Information on residence, type of training and speciality are available from AMA records. A multi-variate analysis of data will be used to determine association of each of these cancers with radiation, infection, or other factors.